The present invention relates to a fan and its impeller, and particularly to the fans capable of reducing windage and noise.
FIG. 1 shows a conventional impeller 100. The impeller 100 includes a hub 102 and a plurality of fan blades 104 directly connected to the hub 102. The frontal surfaces 106 of the fan blades 104 are tangent to the edge of the hub. When the number of fan blades 104 is increased, space between the fan blades 104 is limited, increasing windage and noise of the impeller 100. Conversely, when the number of fan blades 104 is reduced, the total active area of the fan blades 104 is reduced accordingly, thus reducing the airflow efficiency of the impeller 100 of the conventional fan.
Typically, a conventional impeller 100 with thirteen fan blades 104 is employed to balance adequate airflow efficiency without significantly increasing the windage and noise thereof. In a compact electrical device, however, heat dissipation efficiency is enormously required due to the compacted volume thereof, which exceeds the adequate airflow efficiency of the conventional fan with the impeller 100. As a result, a fan with enhanced heat dissipation efficiency and reducing windage and noise thereof is required.